double eraGmst82	(	double	dj1,
		double	dj2
	)

Definition at line 3 of file gmst82.c.

References C, eraAnp(), ERFA_DAYSEC, ERFA_DJ00, ERFA_DJC, ERFA_DS2R, and t.

Referenced by eraGst94(), and t_gmst82().

{
/* Coefficients of IAU 1982 GMST-UT1 model */
   double A = 24110.54841  -  ERFA_DAYSEC / 2.0;
   double B = 8640184.812866;
   double C = 0.093104;
   double D =  -6.2e-6;

/* Note: the first constant, A, has to be adjusted by 12 hours */
/* because the UT1 is supplied as a Julian date, which begins  */
/* at noon.                                                    */

   double d1, d2, t, f, gmst;

/* Julian centuries since fundamental epoch. */
   if (dj1 < dj2) {
      d1 = dj1;
      d2 = dj2;
   } else {
      d1 = dj2;
      d2 = dj1;
   }
   t = (d1 + (d2 - ERFA_DJ00)) / ERFA_DJC;

/* Fractional part of JD(UT1), in seconds. */
   f = ERFA_DAYSEC * (fmod(d1, 1.0) + fmod(d2, 1.0));

/* GMST at this UT1. */
   gmst = eraAnp(ERFA_DS2R * ((A + (B + (C + D * t) * t) * t) + f));

   return gmst;

}

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